Oestrogen concentrations in the faeces of bitches

Few data are available concerning excretion of oestrogen from bitches. During anoestrus, oestrogen concentrations are low in the blood of bitches and, therefore, a sensitive method for measuring concentrations of these hormones by analysis of faeces was developed. Daily faecal samples from bitches (n = 25) of various breeds were analysed (collected for 20 days after the start of pro-oestrous vulvar sanguinous discharge), as well as single samples from bitches in anoestrus (n = 30; samples from 16 of these bitches were also analysed during pro-oestrus and oestrus) and ovariohysterectomized bitches (n = 18). Samples (0.5 g mixed with 0.5 ml water) were extracted and after the samples were cleaned the unconjugated oestrogen content was measured, using a group specific enzyme immunoassay. Oestrone and oestradiol were identified as the predominant immunoreactive oestrogens by HPLC. In samples collected on the first day of pro-oestrous vulvar sanguinous discharge, oestrogen content was 9.3-231.1 nmol kg-1 faeces (median 45.5 nmol oestrogen kg-1 faeces). On day 8 of discharge, oestrogen content was 21.8-539.5 nmol kg-1 faeces (median 114.1 nmol oestrogen kg-1 faeces). Oestrogen content in bitches in anoestrus was 2.2-65.2 nmol kg-1 faeces (median 18.5 nmol oestrogen kg-1 faeces), whereas ovariohysterectomized bitches excreted lower amounts of oestrogens (range 0.7-18.1 nmol kg-1; median 4.4 nmol kg-1). The differences between oestrogen content in ovariohysterectomized bitches and bitches during anoestrus and oestrus were significant (P < 0.001). It is concluded that the method developed in the present study is suitable for monitoring the low production of oestrogens during anoestrus.